Lead a list item with M3's video slot

Plan step 23, containment.md § Missing ("Lists: leading video slot").
`<x-list-item video="…">` (or `<x-slot:video>`) draws M3's leading media
in its landscape sizes: 100×56px in a two-line item, 114×64px in a
three-line one (ListTokens' LeadingVideoSmall 56×100dp and
LeadingVideoLarge 64×114dp), with the small corner the leading image
takes. The tallest element sets an item's height, so a video lifts the
item to at least the 72px two-line row — 56 + 2×8 is 72 exactly, and
64 + 2×12 is 88.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9

resources/views/showcase/sections/containment.blade.php

@@ -60,6 +60,24 @@
                 <x-list-item title="Thirty days" :selected="false" />
             </x-list>
             BLADE,
+        'A list with leading video' => <<<'BLADE'
+            <x-list dividers label="Clips" class="w-full max-w-md">
+                <x-list-item title="Sunrise over the lake" description="2:14 · 48 MB">
+                    <x-slot:video>
+                        <div class="grid place-items-center bg-linear-to-br from-primary-container to-tertiary-container text-on-primary-container">
+                            <x-icon name="play_circle" class="size-6" />
+                        </div>
+                    </x-slot:video>
+                </x-list-item>
+                <x-list-item overline="Draft" title="Walking the old town" description="Uploaded yesterday · 7:48">
+                    <x-slot:video>
+                        <div class="grid place-items-center bg-linear-to-br from-secondary-container to-primary-container text-on-secondary-container">
+                            <x-icon name="play_circle" class="size-6" />
+                        </div>
+                    </x-slot:video>
+                </x-list-item>
+            </x-list>
+            BLADE,
         'Dividers and collapse' => <<<'BLADE'
             <div class="w-full space-y-4">
                 <x-collapse title="How long do links last?" icon="schedule" open>